The levels and turnover rates of norepinephrine, epinephrine, and dopamine and their various metabolites in body fluids reflect to different degrees the level of functions of the aminergic neurones from which the amines are released. Peripheral sympathetic responsivity is reflected in plasma levels of norepinephrine but care must be taken to consider removal rates of the catecholamine. Urinary metabolites of the catecholamines provide a useful means for assessing their overall synthesis in the body while the relative proportion of normetanephrine appears to be related to functional activity. Other indirect indices, based on stimulation of secretion of other compounds (melatonin, pancreatic polypeptide), are also valuable adjuncts in assessing autonomic activity. This project now includes Z01-MH 00275 which it has grown to overlap.